1. Technical Field of the Invention
The present invention relates to a processing apparatus and a processing method for carrying out a designated treatment while supplying a treatment liquid to substrates, such as semiconductor wafers. Particularly, the invention relates to a cleaning technique for the substrates.
2. Description of the Related Art
Generally, in the manufacturing process for semiconductor devices, a cleaning systems is employed in order to remove various contamination adhering to surfaces of the semiconductor wafers, for example, particles, organic contaminants, metal impurities, or the like. On behalf of the cleaning system for cleaning the wafers, there is known a single wafer processing system using a spin type of cleaning apparatus. In the conventional cleaning method, there are also known a scrub cleaning by contact of a rotating member, such as brush or sponge, with a surface of the wafer in rotation, and a jet cleaning by supplying the treatment liquid highly-pressurized by a jet pump to the wafer surface through a jet nozzle.
When employing a pure water of high resistivity in the above jet cleaning, it is indispensable to take a measure to eliminate static electricity from the pure water. If the pure water on the order of 15 to 18 Mxcfx89 in resistivity is supplied to the wafer surface under high pressure of 50 to 100 kgf/cm2, then the wafer takes an electrical charge. Further, when the electrical charge on the wafer exceeds its dielectric strength, there is a possibility that sparks due to static electricity are produced to destroy semiconductor devices built on the wafer, electrostatically.
Accordingly, in the related art shown in FIG. 12, a bubbling unit 102 having carbon dioxide (CO2) bubbled up therein is arranged in the middle of a transporting passage 101 to transport the treatment liquid to a jet nozzle 100, so that the treatment liquid of a carbonated solution (H2CO3) is produced by passing the pure water (DIW) through the bubbling unit 102. After being pressurized into high pressure by a jet pump 103, the carbonated solution on the order of 0.2 Mxcfx89 in resistivity is fed to the jet nozzle 100 and ejected to the surface of a water W. The carbonated solution acts as an ionized water to neutralize the occurrence of static electricity, for preventing the surface of the wafer W from taking an electrical charge.
However, since the transporting passage 101 and the jet pump 103 are both made of metal, such as stainless steel, the flowing of the carbonated solution as a weak acid into the transporting passage 101 and the jet pump 103 causes metallic components (e.g. iron, chromium, nickel, etc.) to dissolve into the carbonated solution at the rate of e.g. 0.1-0.5 ppb. If the carbonated solution containing such metallic components is supplied to the surface of the wafer W through the jet nozzle 100, the wafer W will be contaminated with the components.
Accordingly, it is therefore an object of the present invention to provide a processing apparatus and a processing method, by which it is possible to prevent the substrate to be contaminated with metallic components in supplying the pressurized treatment liquid to the substrate.
According to the first aspect of the invention, the object of the present invention described above can be accomplished by a processing apparatus which includes: a first nozzle for supplying a treatment liquid for applying a designated process on a substrate; a first liquid passage connected to the first nozzle, for transporting the treatment liquid to the first nozzle; a pressurizing mechanism for pressurizing the treatment liquid thereby to feed it to the first liquid passage; a second nozzle for supplying a charge removing liquid to the substrate; and a second liquid passage arranged independently of the first liquid passage and connected to the second nozzle, for transporting the charge removing liquid to the second nozzle.
According to the present invention, since the charge removing liquid is supplied to the substrate via a different route from that for the treatment liquid, the charge removing liquid does not come in contact with the pressurizing mechanism. Therefore, it is possible to prevent metallic components of constituents of the pressuring mechanism from dissolving into the charge removing liquid, preventing the contamination on the substrate.
It is preferable that the second nozzle and the second liquid passage are both made of material which does not dissolve metallic components thereof into the charge removing liquid in spite of the contact of the second nozzle and the second liquid passage with the charge removing liquid.
The second nozzle may supply the charge removing liquid in the form of mist. By connecting a gas passage for supplying gas from a gas source to the second nozzle and mixing the gas with the charge removing liquid passing through the second nozzle, the charge removing liquid can be ejected in the form of mist. Consequently, it is possible to reduce the thickness of a liquid film of the charge removing liquid formed on the substrate, preventing the reduction in processing effect of the treatment liquid.
The charge removing liquid may be identical with a carbonated solution. The carbonated solution can be produced by a dissolving device for dissolving carbon dioxide in a pure water. In this case, the gas to be supplied to the second nozzle may be either carbon dioxide or nitrogen gas.
The dissolving device may include a cell unit into which the pure water is supplied and a hollow thread which is disposed in the cell unit and into which carbon dioxide is supplied. Then, the so-constructed dissolving device is simple in constitution and facilitates its maintenance.
Preferably, the charge removing liquid is fed to the second nozzle by pneumatics without the intermediary of a mechanical pressurizing mechanism, such as a pump. With the arrangement, it is possible to reduce the possibility of the substrate being contaminated in metal.
According to the second aspect of the invention, there is also provided a processing method for a substrate which includes: a first step of supplying a charge removing liquid to the substrate thereby forming a liquid film thereon; and a second step of supplying a pressurized treatment liquid to the substrate having the liquid film of the charge removing liquid formed on the substrate.
In the above method, preferably, the first step is continuously carried out while the second step is carried out. Further, it is also preferable that the charge removing liquid and the treatment liquid are supplied to the substrate through the intermediary of two different liquid passages. In the first step of the above method, preferably, the charge removing liquid in the form of mist is ejected to the substrate. The charge removing liquid may be identical to a carbonated solution.
According to the third aspect of the invention, there is also provided a processing method for a substrate which includes: a step of supplying a charge removing liquid to the substrate thereby forming a liquid film thereon; and a step of supplying a pressurized treatment liquid to the substrate having the liquid film of the charge removing liquid formed on the substrate;
The above and other features and advantages of this invention will become apparent, and the invention itself will best be understood, from a study of the following description and appended claims, with reference had to the attached drawings showing a preferred embodiment of the invention.